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Coherent intermetallic precipitate-strengthened, Fe-Mn-based low-density steels are of interest owing to their superior mechanical properties. We present here the observation of 2-4-nm-sized, Ni-Al-type B2 precipitates localized within the disordered BCC phase, which is embedded in the major FCC structured austenitic (gamma) matrix. Upon exposure to high temperatures of 1110C for 30 min, the B2 phase coarsens, reaching a size of 26 nm while still positioned within the BCC phase. It further disintegrates into ~6-nm sized precipitates upon annealing at 1200C for 30 min indicating the limited stability of the B2 phase. Thermodynamic phase analysis also supports the above observation of decreasing B2 phase stability with increasing temperature beyond 1100C. In addition, APT also revealed the presence of kappa-precipitates localized within the majority gamma matrix. The collective contribution of kappa, B2 and A2 phases strengthens the majority gamma matrix of the hot-rolled steel, resulting in achieving an ultimate tensile strength in excess of 1.2 GPa with an extended ductility of ~34% at room temperature.

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• Creative Commons BY Attribution 4.0 International
  

Keyword: Precipitate localisation, Atom Probe Tomography, Steels

Date published: 2022-06-08

Publisher: Springer

Journal:

• JOM (ISSN: 15431851) vol. 74 issue. 8 p. 3181-3190

Funding:

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4604

First published URL: https://doi.org/10.1007/s11837-022-05349-2

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Updated at: 2024-07-25 12:30:12 +0900

Published on MDR: 2024-07-25 12:30:12 +0900